1. Field of the Invention
The present invention relates to a pentagonal roof prism mounted in a single reflex camera, and more particularly to an improvement of a structure of an optical system provided for indicating information within a viewfinder.
2. Description of the Related Art
Conventionally, there is known an optical system in which a miniature prism is applied to a surface of a pentagonal roof prism, so that information indicated by an indicating device, such as a liquid crystal display, is directed to a viewfinder by the miniature prism. Namely, a light beam corresponding to the indicated information is reflected, by the miniature prism, into the viewfinder, so that information, such as a shutter speed, is indicated within the viewfinder, but outside the frame of an object image.
In such a device, however, stray light, which enters from outside the pentagonal roof prism and becomes internally incident on a surface to which the miniature prism is applied, is reflected by an inner plane of the pentagonal roof prism and is directed to the viewfinder. This stray light causes an outside portion of the frame of the object image, formed in the viewfinder, to fade or become discolored, and thus, viewing of the information, such as shutter speed, by the photographer would become difficult.